LEUKEMIA AND ANEMIA IN AKR O MICE .2. ROLE OF THE SPLEEN AS AN ERYTHROPOIETIC ORGAN DURING LEUKEMIA DEVELOPMENT/

In order to study the role of the spleen in erythropoiesis during AKR/ O leukaemogenesis, we have cultured bone marrow and spleen erythroid c olony-forming units (CFU-E) and burst-forming units (BFU-E) from AKR/O mice (n = 40) with leukaemia of varying severity and type of manifest ation. Mice with leukaemia/lymphoma had reduced concentrations of bone marrow CFU-E and BFU-E as compared to healthy, age-matched AKR/O mice . The spleen content of CFU-E was increased, and highest in mice with a spleen size between 500 and 1000 mg. The largest spleens had a somew hat lower CFU-E content. Mice with the highest spleen CFU-E content mo st often had a normal PCV; however, 4/7 had a normal bone marrow CFU-E concentration. During AKR/O leukaemogenesis with development of splee n enlargement, the spleen may act as an erythropoietic organ, and cont ribute to maintaining a normal PCV. This may be a temporary ability wh ich is reduced or lost with further progress of the disease.